Pharmacopoeia of the People's Republic of China (2010; p. 197) records that Siraitiae fructus is sweet in flavor and cool in property, and it belongs to the lung and large intestine meridians, it can reduce fever, moisturize the lungs, relieve sore throat and restore voice, and it also functions as a laxative. Siraitiae fructus is commonly used to treat cough caused by lung heat, sore throat, voice loss, and constipation. Modern research shows that Siraitiae fructus contains tetracyclic triterpenoid saponins, and especially, it has a high content of mogroside V. Therefore, Pharmacopoeia of the People's Republic of China requires that Siraitiae fructus be calculated as dry goods, and should contain no less than 0.50% of mogroside V. The sweetness of Siraitiae fructus is about 300 times of sucrose; it is not easily dissolved by the human digestive system and thus provides limited calories. Due to its safe and stable properties, Siraitiae fructus and its extracts are gradually becoming an ideal food for people having diabetes and obesity.
Because fresh Siraitiae fructus is difficult to store and transport, dried Siraitiae fructus has historically been consumed as both food and herb. However, three main concerns exist when people consume dried Siraitiae fructus: (1) it is difficult to control dosage. Siraitiae fructus has a high degree of sweetness, thus a low dosage would result in a not sweet enough taste, while a high dosage would affect the taste due to too much sweet. Furthermore, the sweetness in Siraitiae fructus varies a great deal due to factors such as breeds, origins, drying methods, harvesting time, etc. Therefore, both the inexperienced and the experienced technicians need to perform preliminary experiments to determine the proper dosage for each batch of Siraitiae fructus; (2) it is difficult to maintain the taste. Fresh Siraitiae fructus is a fragrant and genuinely sweet fruit. Because it has a dense and tight fruit peel, roasting under high-temperature for a longtime is required to obtain dried Siraitiae fructus. However, even dried Siraitiae fructus processed with high-level roasting techniques still has a strong sweet flavor and some degree of burnt odor, due to the drying process. Moreover, most dried Siraitiae fructus products are processed by fruit farmers in their simple and crude ovens; the flesh usually is roasted to dark brown color, and has a distinct burnt taste and a bitter flavor. Dried Siraitiae fructus made from dead Siraitiae fructus or unripe Siraitiae fructus fruit would have an even worse taste; (3) it is difficult for consumers to determine whether to accept or to discard the fruit peel. The Siraitiae fructus fruit peel itself does not have an obvious sweetness. However, through the drying process under high temperature, part of the flesh liquefied and passed to the peel through capillary action or dripping on the peel, resulting that the peel has a markedly sweet taste. This confuses consumers in that they are not certain whether the peel can be consumed or not. It would be a waste to discard the peel because it is sweet regardless; however, some consumers cannot accept the peel because it is dark and fluffy, and seems dirty. Due to the above concerns, it often happens that consumers would steep a half or full dried Siraitiae fructus fruit in several hundred milliliters of water. The taste is acceptable at the beginning; as the amount of water reduces, however, the amount of dissolved Siraitiae fructus increases. This causes the Siraitiae fructus solution to have a stronger degree of sweet taste, burnt odor, and bitter flavor, and also gives the solution a darker color, and resulted in the eventual discard of the Siraitiae fructus solution.
With the gradual familiarization and recognition of its function as a dietary supplement, as well as the advance in food and drug processing techniques, products containing Siraitiae fructus as the main ingredient are emerging. Until now, 137 invention patents relating to Siraitiae fructus can be found in the patent information database of the State Intellectual Property Office of the People's Republic of China. Of those, 55 patents relate to food or dietary supplement products, including: 14 patents directed at fruit wine or fruit vinegar containing Siraitiae fructus and other ingredients; 8 patents relate to solid products containing original plants, exemplified by tea, that are made from Siraitiae fructus and other ingredients; 12 patents relate to dissolvable solid food or low-calorie sweetener that contains Siraitiae fructus and other ingredients; and 7 patents relate to products comprising Siraitiae fructus as the only ingredient.
Of all the edible materials, not many drinks made from one single ingredient are good in color, smell, and taste; Siraitiae fructus is one of the few. Obviously, it would damage the characteristics of Siraitiae fructus if it is used as a common ingredient together with other materials in a formula to produce an end product.
In one of the 7 patents that relate to products containing only Siraitiae fructus, i.e., patent application number 200610021160.X, titled “Siraitiae fructus product and method for preparing same”, relates to a drying process where Siraitiae fructus flesh is pulp and then coated on a roasting device for drying; patent application number 200510020314.9, titled “fresh Siraitiae fructus powder and preparation method thereof”, relates to a process where fresh Siraitiae fructus is freeze dried and pulverized; patent application 200810174726.1, titled “method for preparing fresh Siraitiae fructus freeze-dried superfine powder”, relates to a process where pre-frozen, pulverized Siraitiae fructus is vacuum dried at a temperature of between 40° C. and 120° C., and then super-fined; patent application number 200910114443.2, titled “Fructus momordicae instant powder and preparation method thereof”, relates to treating Siraitiae fructus extract with several enzymes before drying; patent application number 200810001670.X, titled “Siraitiae fructus sweetener and preparation method”, relates to extracting dry powder from whole Siraitiae fructus and mixing the same with mogroside at different ratios; patent application number 200510066542.X, titled “Preparation method for Siraitiae fructus juice”, relates to filtering, press filtering, micro-filtering, and nano-filtering Siraitiae fructus juice to produce liquid drinks; patent application number 200810097509.7, titled “De-colored Siraitiae fructus juice and method for preparing the same”, relates to de-coloring Siraitiae fructus juice with resin, and then acidifying it to produce a white or yellowish transparent liquid.
Compared with other compound products, these seven patented products have advantages in keeping and displaying the characteristics of Siraitiae fructus, and improving the homogeneity of product quality. However, they still have obvious drawbacks: (1) the last two patented products are liquid preparations; complex processing techniques are required; and preservatives are added to conserve the products; (2) the fourth and fifth patented products have a high degree of sweetness and are inconvenient to use. Dry powder made from Siraitiae fructus water is about 20 times sweeter than sucrose. A further fine preparation causes dry powder to have a mogroside V content of 30%, and that is about 100 times sweeter than sucrose. Suppose a consumer prepares a 200 ml drink, only 15 g of sucrose would be needed to achieve an ideal degree of sweetness. However, if Siraitiae fructus extract is used as the sweetener, then only 0.75 g of Siraitiae fructus extract powder is needed, and only 0.15 g of crude saponin powder is needed. Such a small amount is inconvenient for packaging and usage; (3) the first three patented products are obtained from directly pulverizing fresh Siraitiae fructus, and then drying. Although properties such the degree of sweetness and the ability to absorb moisture of these products are not as good as those of the fourth and fifth patented products, they are feasible in terms of packaging and determining quantity. However, there still exist three disadvantages: (1) in these products, the non-edible Siraitiae fructus peel and seeds are pulverized together with flesh and end up being ingested by consumers. The impure contents from the peel render a high level of microorganisms in the final products, and the fatty acids from the seeds render the products an unpleasant odor and make the final products susceptible to rancidity; (2) when dried under low-temperature conditions, Siraitiae fructus enzyme activities are well-kept, thus rendering the final product a numbing feeling; and (3) whole fruit powder products have a lot of suspended and precipitated substances, rendering the liquid solution an unaesthetic appearance.